The present invention is directed to formulations and methods of treating malnutrition associated with chronic lung diseases. Chronic lung diseases include diseases such as chronic obstructive pulmonary disease (COPD), cystic fibrosis and interstitial lung disease. A common characteristic of these diseases is the decreased capacity of lungs to exchange oxygen and carbon dioxide. This causes the patient to breathe faster which increases the energy the patient must expend in order to obtain enough oxygen.
Malnutrition is a common complication in these patients resulting from the increased energy needed to breathe as well as the reduced oral intake of food. This often results in weight loss which leads to a decline in pulmonary function. Severe weight loss is associated with a poor prognosis and increased mortality. Sukumalchantra, et al. Am. J Med, 39:941-945 (1965); Vandenbergh, et al., Am Rev Respir Dis, 95:556-566 (1967); Burrows, et al., Am Rev Respir Dis. 91:665-678 (1963); and Tiech, S., Chest. 85:635-665(1984).
Nutritional repletion regimens have been used in order to improve pulmonary function of patient's having chronic lung diseases. However, the physiologic response of individuals who suffer from these diseases pose significant challenges. This is particularly the case since the metabolism of certain nutrients, especially carbohydrates, used in these regimens results in both increased metabolic demands and ventilatory requirements due to excessive quantities of CO.sub.2 produced from the metabolism of carbohydrates.
Goldstein, et al. Chest, 91:222-224 (1987) studied the energy expenditures of patients with COPD. Two hypercaloric formulations for use in refeeding patients with malnutrition were compared; a carbohydrate-based formulation consisting of a calorie distribution of 53% carbohydrate, 30% fat and 17% protein, and a fat-based formulation consisting of 55% fat, 28% carbohydrate and 17% protein. The patients were administered these two hypercaloric nutritional supplements in amounts equivalent to 1.7 times the amount of calories measured by the patients' resting energy expenditure (REE). Goldstein et al. concluded that diet-induced increases in energy expenditure occurred in patients with COPD and were accentuated by a moderately high carbohydrate diet.
In a later publication, Am. Rev. Resp. Dis., 138, pp. 636-644 (1988), utilizing the same two hypercaloric formulations Goldstein et al. demonstrated that increased body weight, nitrogen balance and muscle strength were obtained by nutritional supplementation of 1.7 times the resting energy expenditure. This study also illustrated the problem of increased metabolic demand and ventilatory requirements associated with carbohydrate supplementation.
As the above studies show, the CO.sub.2 produced from the metabolism of carbohydrate used for nutritional repletion decreased the patient's overall respiratory function and complicated ventilatory management. The decrease in respiratory function that occurred from these prior nutritional repletion regimens could be so severe that patients treated with aggressive hypercaloric nutritional regimens with high carbohydrate levels have been known to lapse into respiratory distress from the high levels of CO.sub.2. Askanazi, et al. Surgery, 87:596-598 (1980) described a case of respiratory distress due to the high carbohydrate load of a total parenteral nutrition (TPN) formulation.
The foregoing studies demonstrate that patients with chronic lung diseases have altered metabolic states which require careful selection of the components used in nutritional formulations. Furthermore, traditional hypercaloric nutritional supplementation formulations, as demonstrated above, must be adjusted for the specialized needs of patients who suffer from chronic lung diseases. Thus, there exists a continuing need for nutritional formulations to treat chronic lung diseases and induce the beneficial effects associated therewith.